1. Field of the Invention
The present invention relates to a data transmission system and, more particularly, to a data transmission system and method adapted to simultaneously transmit a differential signal pair and a common signal through a differential signal line pair. A claim of priority is made to Korean Patent Application No. 2003-75269 filed Oct. 27, 2003 in the Korean Intellectual Property Office, the disclosure of which is hereby incorporated by reference in its entirety.
2. Description of the Related Art
A conventional data transmission method is characterized by separate approaches to the transmission of a so-called “single or common” signal and a differential signal pair. Namely, the method transmits the single signal through a single signal line, but transmits the differential signal pair through a differential signal line pair. The differential signal pair includes one signal having a voltage level higher than a reference voltage and another signal having a voltage lower than the reference voltage. As a result, when single bit data is transmitted, the differential signal pair approach to data transmission twice as many data lines, as compared with the single signal approach to data transmission.
Thus, a method of transmitting data that uses the common signal approach is able to transmits more data than a method using a differential signal pair approach for a given number of signal lines. However, in applications wherein a data signal is transmitted at a high frequency, common signal methods of transmission are highly sensitive to a noise. In contrast, method of data transmission using the differential signal pair approach enjoy relatively strong noise immunity. Thus, both approaches to data transmission have relative benefits and disadvantages.
The relative benefits of common signal transmission methods notwithstanding, most contemporary data transmission methods use a differential signal pair approach to data transmission because data accuracy is of paramount importance, and both the quantity data and the speed with which data is transmitted are constantly increasing. Accordingly, transmission noise is a consistent problem, and conventional data transmission systems typically include the numerous signal lines required to implement a differential signal pair approach to data transmission.
Thus, where a method of transmitting a differential signal pair is used, a corresponding system board will include at least twice as many signal lines as the number of data bits being transmitted by the system. In actuality, more signal lines are required in a competent data transmission system. For example, one or more data strobe signal(s), (i.e., a clock signal that is used as a reference signal controlling data input/output (I/O) operations) is typically transmitted by the system for a grouping of data bits. In current implementations, a 32-bit I/O device mounted on a system board might additionally transmit one data strobe signal per each respective grouping of 4, 8, or 16 bits of data.
Additional signal lines necessitate an increased pin count for related transmission devices, and lead to increased probabilities of manufacturing errors in increasingly crowded system boards. In sum, the number of signal lines required to conventionally transmit data using a differential signal pair approach, taken together with the additional overhead signal lines required to transmit control signals, such as data strobe signals, is simple too great. Manifest implementation and operational improvements would arise from a reduced number of signal lines in data transmission systems.